California braces for week of El Niño storms, mudslides, flash floods

A steady stream of El Niño–fueled rain and snowstorms is forecast to batter California this week, prompting the Red Cross to mobilize its entire Pacific Coast staff on Tuesday because of the threat of mudslides and flash flooding.

“We’re looking at potentially heavy rain all along the coast, from Redding [in Northern California] to Los Angeles. It’s really a very extensively stormy week, and I do expect to see localized flooding, mudslides, mountain snow and travel delays, which could be problematic for our logistics,” said Brad Kieserman, the vice president of disaster operations and logistics for the Red Cross.

“We’ve put out a prepare-to-deploy order for our entire staff on the Pacific Coast so that they’re ready to mobilize,” he said.

The conveyor belt of storms will bring several inches of rain and thunderstorms, as well as high-surf advisories to low-lying coastal areas, in the drought-stricken state this week, according to the National Weather Service. High-elevation areas are expecting to get snow.

The wet weather — energized by El Niño, a pattern of warmer-than-usual surface water in the eastern equatorial Pacific — was expected to move across California in “multiple bursts,” the National Oceanic and Atmospheric Administration said on its website.

Much of the severe weather in the southern United States in recent weeks — including flooding and a spate of winter tornadoes that killed at least 22 people — has been made stronger by the warm, moist air brought north as a result of El Niño. Compared with the last strong El Niño, in 1997 and ’98, this El Niño has been made even more powerful by ocean warming caused by climate change.

Emergency officials said the risk in California is growing this year.

“I do see it as a serious threat,” Kieserman said, adding that the Red Cross has been working with state emergency officials and municipal partners in potentially affected counties.

“This is more activity from El Niño, driving these flooding rains and mountain snows that will be in California all this week. The rain ... really creates a significant risk of floods, flash floods, mudslides and landslides, especially in areas with erosion resulting from recent wildfires,” he said.

A voluntary evacuation order went into effect at 10 a.m. local time on Tuesday for residents of Silverado Canyon in Southern California’s Orange County because of potential flash floods and mudslides, the county’s Emergency Operations Center said.

Silverado Canyon’s steep slopes were scorched in a 2014 wildfire, and the National Weather Service on Tuesday issued a flash flood watch for the area.

The Red Cross has set up a shelter for anyone displaced in Orange County and opened one Tuesday morning in Ventura County after the county issued a voluntary evacuation order for the Camarillo Springs area, which was also hit by wildfire, Kieserman said.

Even modest rainfall can trigger mudslides and flash floods in steep, recently burned areas because rain and soil that would normally be absorbed and held in place by vegetation can become torrents carrying debris.

The U.S. Geological Survey has conducted hazard assessments for post-wildfire debris flows in four recently burned areas in Southern California. The agency found a high probability of mudslides and flash floods in Orange, Los Angeles and Ventura counties, the U.S. Geological Survey said.

Rain and snow were expected to taper off by Friday, according to forecasters. As the weather pattern moves inland, it is expected to bring rain to the Midwest and snow to the Great Lakes area by Wednesday, the National Oceanic and Atmospheric Administration said.

As much as 15 inches of rain could fall in the next 16 days in Northern California, with about 2 feet of snow expected in the highest points of the Sierra Nevada, said Johnny Powell, a forecaster with the National Weather Service.

In Southern California, between 2 and 3.5 inches of rain is predicted to fall across the coastal and valley areas, and up to 5 inches falling in the mountains.